This invention relates to bearings of the type comprising a plurality of pivoted bearing shoes positioned to engage a slide member in supporting relation thereto, wherein oil is applied to the bearing faces of the shoes to establish a hydrodynamic wedge of oil created by the motion of the slide member. The invention is applicable to trunnion bearings for cylindrical journals and also to slider bearings in which the slide member has a flat bearing face.
The performance of bearings of this type depends upon a number of geometric factors, one of the most important factors being the disposition of the bearing face of each shoe in relation to its respective pivot. For optimum performance the pivot must be located slightly off centre towards the trailing edge of the shoe. It follows that the performance of such a bearing will be optimized for one direction of travel only of the slide member, i.e. journal or runner; if the geometry is optimized for one direction of travel, the performance of the bearing will be inferior when the direction is reversed, as the pivot will then be offset towards the leading edge of the shoe. When bidirectional motion is required it is usual to compromise by mounting the bearing shoe symmetrically with respect to its pivot. However, with this arrangement the bearing performance cannot be optimized for either direction of travel, and indeed the performance is unpredictable.
In order to meet this problem it has been proposed to provide a journal bearing shoe arrangement in which the effective pivot location of the bearing shoe can be changed by changing the pressure profile of the lubricating oil film at the interface between the bearing pad and the journal which it supports. Such an arrangement is described in U.S. Pat. No. 3,887,245 of Keith E. Rouch, dated June 3, 1975. A very much more complex bearing shoe arrangement intended to solve this problem is also described in U.S. Pat. No. 3,917,365 of Raymond C. Jenness, dated Nov. 4, 1975.